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Chapters

0:00 Introduction
0:59 Duration
1:21 Severity of height of fever
1:54 Pattern
2:50 Causes of Pyrexia
3:35 Symptoms of Pyrexia
3:55 Diagnosis and treatment of Pyrexia
4:24 Treatment for Pyrexia




Fever, also referred to as pyrexia, is defined as having a temperature above the normal range due to an increase in the body's temperature set point.[5][6][12][7] There is not a single agreed-upon upper limit for normal temperature with sources using values between 37.2 and 38.3 °C (99.0 and 100.9 °F) in humans.[1][7][8] The increase in set point triggers increased muscle contractions and causes a feeling of cold or chills.[2] This results in greater heat production and efforts to conserve heat.[3] When the set point temperature returns to normal, a person feels hot, becomes flushed, and may begin to sweat.[3] Rarely a fever may trigger a febrile seizure, with this being more common in young children.[4] Fevers do not typically go higher than 41 to 42 °C (106 to 108 °F).[6]

A fever can be caused by many medical conditions ranging from non-serious to life-threatening.[13] This includes viral, bacterial, and parasitic infections—such as influenza, the common cold, meningitis, urinary tract infections, appendicitis, Lassa, COVID-19, and malaria.[13][14] Non-infectious causes include vasculitis, deep vein thrombosis, connective tissue disease, side effects of medication or vaccination, and cancer.[13][15] It differs from hyperthermia, in that hyperthermia is an increase in body temperature over the temperature set point, due to either too much heat production or not enough heat loss.[1]

Treatment to reduce fever is generally not required.[2][9] Treatment of associated pain and inflammation, however, may be useful and help a person rest.[9] Medications such as ibuprofen or paracetamol (acetaminophen) may help with this as well as lower temperature.[9][10] Children younger than three months require medical attention, as might people with serious medical problems such as a compromised immune system or people with other symptoms.[16] Hyperthermia requires treatment.[2]

Fever is one of the most common medical signs.[2] It is part of about 30% of healthcare visits by children[2] and occurs in up to 75% of adults who are seriously sick.[11] While fever evolved as a defense mechanism, treating a fever does not appear to improve or worsen outcomes.[17][18][19] Fever is often viewed with greater concern by parents and healthcare professionals than is usually deserved, a phenomenon known as fever phobia.[2][20]